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Stanford Medicine 25 Blog

Pulsus Paradoxus & Blood Pressure Measurement

Blood pressure is an important vital sign. Measurement errors are common so it is important to understand factors that affects results. Pulsus paradoxus is a very sensitive and valuable tool to diagnosis or ruling out cardiac tamponade.

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Introduction to Measuring Blood Pressure

Few realize that the measurement of blood pressure is highly skill-dependent. A practiced technique allows a physician to take an accurate reading when the result may guide clinical decision making. Below are some steps to help make an accurate measurement.

Blood Pressure Measurement

Position

Recognize that BP normally rises with activity/exertion. Therefore, BP should never be taken shortly after ambulation, such as when a patient first walks into clinic. If checking orthostatic vital signs, the individual should ideally be in the position (supine, sitting, or standing) for at least 60 seconds before the measurement is recorded.

Caveats: BP norms are taken from quiet patients sitting with back support. Speaking may elevate BP by 8-15mmHg (Arch Intern Med 153:2741), sitting w/o back support may elevate BP by 5-10mmHg (J Gen Intern Med 10:223).

Equipment

Cuff size: Bladder length should be 80% and bladder width should be at least 40% of the circumference of the upper arm.

A too small cuff will overestimate, too large will be ineffective.

Technique

Inflate the bladder quickly to 20 mmHg above the pressure at which radial pulse is blocked.

Deflate the bladder 3 mmHg/sec, record the pressure at which the first Korotkoff sound is heard as the systolic pressure.

Do NOT use upward deflections on the manometer to measure systolic pressure.

Continue deflating, record the disappearance of Korotkoff sounds as the diastolic pressure.

If the Korotkoff sounds are weak, have the patient raise the arm, open and close the hand five to ten times, and then inflate the bladder quickly.

Recordings

Note the pressure, patient position, arm, and cuff size:

e.g. 140/90, seated, right arm, large adult cuff.

Historical Perspective of Blood Pressure Measurement

The first measurement of blood pressure what recorded in 1711 by Reverend Stephen Hales using a glass tube he inserted into the artery of a horse. The first truly accurate measurement of blood pressure in man was not until 1856 when the surgeon Faivre connected a mercury manometer to an exposed femoral artery during limb amputation. In that same year, Karl Vierordt used pressure to obliterate the radial pulse to approximate blood pressure non-invasively for the first time. This technique was greatly advanced by Etiennes Jules Marey who used the mercury manometer to record systolic pressure non-invasively.

Measuring Pulsus Paradoxus

Other Signs of Cardiac Tamponade

Beck's Triad

Low arterial blood pressure

Distended Jugular Veins

Distant, muffled heart sounds

Kussmaul's sign

Distention of jugular veins with inspiration

Seen in: constrictive pericarditis most commonly but also in cardiac tamponade and right ventricular heart failure

Friedreich's sign

exaggerated drop in diastolic central venous pressure

Consult the Expert

Dr. Ronald Witteles

Dr. Ronald Wittelesis certified in Internal Medicine and Cardiology. He serves as the Stanford Internal Medicine Program Director, Associate Director of the CCU and Co-Director, Stanford Amyloid Center.

Clinical Pearl

When testing for pulsus paradoxus, simply focus on the korotkoff sounds. There is no need to watch the patient's respirations.